1. Field of the Invention
The invention relates to an image display system, and device and method for using this system.
2. Description of the Related Art
In image display systems, it is desirable to reduce the amount of information that is needed to represent images. One technique to achieve this is the use of a color look-up table (CLUT) which is used particularly in systems that generate computer graphics images. In this case, one represents the color value of each pixel in an image by an index value that points to a color value stored in the CLUT. When a color value is needed, the index value is used to retrieve the color value from the CLUT.
The palette of colors that is available in the CLUT is preferably much smaller than the total number of conceivable color values. Thus, the amount of information needed to represent an index value is smaller than the amount of information that is needed to represent an arbitrary color value.
Of course, the price of this is that the representation by index values of an arbitrary original image is only approximate: there will be differences between the color values of the original image and the representation. When such a representation is used to display the arbitrary image, the differences will show up as high frequency noise. In addition, there may be systematic color errors (low frequency noise), but these can be eliminated by dithering techniques.
In some display systems, in particular, in video or television display systems, colors for display are represented by YUV values, that is, a luminance component Y and color difference components UV, as standardized by the CCIR. When YUV values are used, a higher spatial resolution is preferably used for the Y component than for the UV components. Typically, separate Y values are used for different pixels, whereas the UV components are the same for pairs of adjacent pixels.
The YUV components corresponding to different colors may be stored in a CLUT, but of course this is merely a matter of representation; it does not affect the noise caused by using a CLUT.